The developing rat cerebellum will be used as a model neural tissue to analyze effects of a variety of stresses known to influence growth of development of human brain. Cerebellum is to be used because of the detailed understanding of morphology and physiology in the adult. Rat is used because of the relative immaturity at birth, ease of animal care and the detailed information and methods available from previous studies of normal development by the principal investigator. Various protocols of X-irradiation will be employed to destroy selectively in graded amounts the population of cerebellar microneurons, thus mimicing viral and drug induced damage to the immature nervous system. Electrophysiological tests will detect the abnormal neuronal interconnections resulting from this graded destruction of interneurons by postnatal X-irradiation. A study will be made to determine what altered elemental motor patterns appear correlated with the morphological and electrophysiological changes in the cerebellar cortex. Studies of effects of malnutrition on brain development will investigate the relative sensitivity of cerebellar development to this stress during the postnatal growth phase. Comparisons will be made with development stress induced by drugs and hormonal imbalance. This comparative analysis of stress studied in detail on the cerebellum as a model neural tissue will contribute to an understanding of general alterations possible in brain growth and for eventually determining corrective procedures.